Method and arrangement for preventing gas from leaving an opening of a vessel

ABSTRACT

An arrangement ( 10 ) for preventing egress of a gas from a first opening of a vessel, the vessel including at least one other opening through which the gas can leave the vessel, the arrangement comprising an open passage ( 48 ) extending substantially around the first opening, the open passage ( 48 ) receiving a flow of gas such that the flow of gas leaves the open passage and flows towards and into the vessel to cause a gas from the environment external to the vessel to be drawn into the vessel. The arrangement may comprise a Coanda surface. The arrangement may be in the form of an inert for placement in the opening to the furnace.

TECHNICAL FIELD

The present invention relates to a method and an arrangement forpreventing egress of gas from a first opening of the vessel.

BACKGROUND ART

Furnaces are used in a wide range of metallurgical processes. Manyfurnaces include a first opening through which feed materials can be fedto the furnace and a second opening through which an exhaust gas or fluegas can be removed from the furnace, as well as other openings for finalproducts and by-products to be recovered. Typical materials that are fedto furnaces in metallurgical processes include concentrates or ores,fluxes, fuel such as coal or coke, and air or oxygen. The feed materialsundergo reaction with the contents of the furnace to produce desirablemetallurgical products. Exhaust gases are produced during the processand the exhaust gases are removed through the exhaust outlet of thefurnace. Dust generated from the feed material descending in the furnacecan also find its way passing with the exhaust gases and removed throughthe exhaust outlet.

One type of furnace that is finding increased use in metallurgicalprocessing is the top entry submerged lance furnace. Top entry submergedlance furnaces comprised a furnace body or vessel. A feed opening isprovided in the top of the furnace. An exhaust opening is providedlaterally of the feed opening. Furnace feed material is passed to thefurnace through the feed opening. A lance is inserted through a separateopening into the furnace. A gas and, optionally, a fuel, are passedthrough the lance into the furnace. The tip of the lance extends intothe molten contents of the furnace. Injection of gas through the lanceagitates the molten contents of the furnace and promotes themetallurgical reactions. The exhaust gases produced by the metallurgicalprocess exit the furnace through the exhaust opening. One type of topentry submerged lance furnace is sole by the present applicant under theISASMELT™ trade mark.

Operating personnel are frequently required to be physically presentclose to the feed opening of the furnace. Therefore, it is desirablethat gases or dust from the furnace do not exit the furnace through thefeed opening. However, in practice, it can be difficult to preventfurnace gases or dust exiting through the feed opening.

It will be clearly understood that, if a prior art publication isreferred to herein, this reference does not constitute an admission thatthe publication forms part of the common general knowledge in the art inAustralia or in any other country.

SUMMARY OF INVENTION

The present invention is directed to a method for preventing egress ofgas from an opening in a vessel and to an arrangement for preventingegress of gas from an opening in a vessel which may at least partiallyovercome at least one of the abovementioned disadvantages or provide theconsumer with a useful or commercial choice.

In one aspect, the present invention provides a method for preventingegress of gas from a first opening of a vessel, the vessel including atleast one other opening through which the gas can leave the vessel, themethod comprising supplying a flow of gas to an open passage extendingsubstantially around the first opening and causing the flow of gasleaving the open passage to flow towards and into the vessel whereby agas from an environment external to the vessel is caused to be drawninto the vessel, wherein a total flow of gas into the first openingsubstantially prevents gas from leaving the vessel through the firstopening.

In a second aspect, the present invention provides an arrangement forpreventing egress of a gas from a first opening of a vessel, the vesselincluding at least one other opening through which the gas can leave thevessel, the arrangement comprising an open passage extendingsubstantially around the first opening, the open passage receiving aflow of gas such that the flow of gas leaves the open passage and flowstowards and into the vessel to cause a gas from the environment externalto the vessel to be drawn into the vessel.

In some embodiments, the open passage extends around the first opening.Throughout this specification, the term “open passage extendingsubstantially around the first opening” should be considered to includea single passage extending around the first opening, a single passageextending almost completely around the first opening and a plurality ofseparate passages having ends that are closely spaced to an end of anadjacent passage such that gas leaving the separate passages causes aninflow of gas that flows inwardly across the circumferential orperipheral extent of the first opening.

In one embodiment, the first opening comprises a generally circularopening. The open passage may comprise an annular open passage extendingaround the first opening. However, the present invention can be modifiedto suit any shaped first opening.

In one embodiment, the open passage extends around an inner surface ofthe first opening.

The surface of the first opening between the open passage and the vesselmay be shaped to promote the flow of gas leaving the open passage toflow towards and into the vessel. In one embodiment, the surface of thefirst opening between the open passage and the vessel may have a shape,when moving in a direction towards the vessel, that extends inwardlytowards the centre of the first opening and then outwardly away from thecentre of the first opening.

In one embodiment, the surface of the first opening between the openpassage and the vessel may form a venturi.

In one embodiment, the surface of the first opening between the openpassage and the vessel comprises a Coanda surface.

In some embodiments, the open passage is in fluid communication with aplenum chamber. The plenum chamber may extend around the first opening.The plenum chamber receives pressurised gas. The pressurised gas flowsfrom the plenum chamber through the open passage and into the vessel.

The plenum chamber may have at least one, preferably two or more, inletsfor receiving pressurised gas. In embodiments where the plenum chamberhas two or more inlets for receiving pressurised gas, the two or moreinlets are preferably equi-spaced around the plenum chamber.

The vessel may comprise any vessel that has a first opening and at leastone other opening through which gas can leave the vessel. The vessel maycomprise a process vessel or a storage vessel. The vessel may comprise ahigh-temperature vessel. The vessel may comprise a furnace. The vesselmay comprise a top entry submerged lance furnace.

The arrangement may further comprise a feed chute for feeding materialto the vessel. The material that is fed to the vessel may compriseparticulate material. The feed chute may also allow a lance to beinserted therethrough to enable the lance to be inserted into thevessel.

The particulate material that is fed to the vessel may be selected fromconcentrate, sand, rocks, aggregates, coal, coke, industrial minerals,limestone, cement, fluxes, man-made materials such as super phosphate,fertilizers, pharmaceuticals, foodstuffs, chemicals, and other naturalmaterials or natural materials such as cereals such as wheat, barley,rice, oats, corn etc.

In some embodiments, the arrangement of the present invention comprisesan insert that is inserted into the first opening of the vessel. Whenthe insert is inserted into the first opening, the inner surface of theinsert effectively defines the first opening of the furnace.

In one embodiment, the insert includes a portion extending into thefirst opening of the vessel and another portion that defines the openpassage extending around an inner periphery of the insert. The insertmay also define the plenum chamber and the at least one inlet forreceiving pressurised gas. The insert may comprise a flange that comesinto contact with an outer surface around the first opening of thevessel to thereby position the insert relative to the first opening ofthe vessel.

The arrangement in accordance with the present invention may be used toprevent egress of furnace contents from a number of furnace openings.For example, if a furnace is provided with two openings (such as a feedopening and a separate lance opening), each of the openings may beprovided with their own arrangement in accordance with the presentinvention. In this manner, the arrangement provided in each opening mayprevent egress of furnace contents from each opening. The skilled personwill appreciate that the furnace will also include an exhaust system andexhaust gases will be removed from the furnace through the exhaustsystem. The exhaust system will typically include an exhaust opening andappropriate ducting/pipework. It is also possible that an arrangement inaccordance with the present invention may be provided to only one of theplurality of openings to the furnace. Other openings of the furnace maybe provided with conventional extraction equipment to prevent furnacecontents coming into contact with operators. For example, the feedopening may be provided with an arrangement in accordance with theinvention and the lance opening may be provided with conventionalextraction equipment.

The furnace may have even more openings. The skilled person may chooseto have only one of the openings to the furnace fitted with thearrangement in accordance with the present invention for preventingegress of furnace contents from that one opening, with other openings tothe furnace thing fitted with conventional extraction equipment.Alternatively, the skilled person may choose to have two or more, oreven all of the openings to the furnace (excluding the exhaust opening)fitted with the arrangement of the present invention for preventingegress of furnace contents from those openings.

Any of the features described herein can be combined in any combinationwith any one or more of the other features described herein within thescope of the invention.

BRIEF DESCRIPTION OF DRAWINGS

Various embodiments of the invention will be described with reference tothe following drawings, in which:

FIG. 1 shows a perspective view from above of an arrangement inaccordance with one embodiment of the present invention;

FIG. 2 shows a perspective view from below of the arrangement shown inFIG. 1;

FIG. 3 shows a side view of the arrangement shown in FIG. 1;

FIG. 4 shows a plan view of the arrangement shown in FIG. 1;

FIG. 5 shows a cross sectional view taken along section lines H-H shownin FIG. 4;

FIG. 6 shows a perspective view of an inner part of the arrangementshown in FIG. 1;

FIG. 7 shows a perspective view of an outer part of the arrangementshown in FIG. 1;

FIG. 8 shows a plan view, partly in cross-section, of the arrangementshown in FIG. 1;

FIG. 9 shows a schematic view of the arrangement shown in FIG. 1 beingmounted to a feed opening of a top entry submerged lance furnace;

FIG. 10 shows a schematic view of one arrangement as shown in FIG. 1being mounted to a feed opening of a top entry submerged lance furnaceand another arrangement as shown in FIG. 1 being mounted to a lanceopening of the furnace;

FIG. 11 shows a schematic view of one arrangement as shown in FIG. 1being mounted to a feed opening of a top entry submerged lance furnaceand a lance opening of the furnace being provided with a conventionalextraction system;

FIG. 12 shows the results of modelling conducted on a top entrysubmerged lance furnace that is essentially similar to the furnace shownin FIG. 10, but with the arrangements 10 fitted to the feed opening andlance opening not being in operation; and

FIG. 13 shows the results of modelling conducted on the top entrysubmerged lance furnace shown in FIG. 12, but with the arrangements 10fitted to the feed opening and lance opening being in operation.

DESCRIPTION OF EMBODIMENTS

The person skilled in the art will appreciate that the attached drawingshave been provided for the purposes of illustrating preferredembodiments of the present invention. Therefore, it will be understoodthat the present invention should not be considered to be limited solelyto the features as shown in the attached drawings.

The arrangement for preventing egress of gas from a vessel as shown inthe attached drawings is designed to be used in the feed opening of atop entry submerged lance furnace. The feed opening of a top entrysubmerged lance furnace is in the top surface of the furnace. In thisembodiment, pressurised gas passes through an annular open passageextending around an insert arrangement that, when inserted into the feedopening, effectively forms the feed opening of the furnace. The gasleaving the annular passageway moves downward into the vessel and causesgas from the environment external to the vessel to also flow into thevessel. The gas leaving the annular passage comprises a gas streamhaving a relatively low (volumetric) flow rate but having a relativelyhigh speed. The combination of the injected gas and the entrained gasfrom the external atmosphere causes a total flow of gas into the feedopening of the furnace that is sufficient to prevent gas within thefurnace from exiting the furnace through the feed opening.

The arrangement 10 shown in the attached figures is designed as aninsert that is inserted into the feed opening of a furnace. The feedopening is typically a generally circular or oval inlet or port. Theinsert 10 includes a lower cylindrical projection 12 that is sized tofit snugly into the feed opening of the furnace. A flange 14 extendsaround the outer surface of the insert 10 above the lower cylindricalprojection 12. When the lower cylindrical projection 12 of the insert 10is inserted into the feed opening, the flange 14 rests on the topsurface of the furnace surrounding the feed opening. This acts toposition the insert 10 relative to the feed opening. Other arrangementsmay be used to position the insert relative to the feed opening.

A generally cylindrical body portion 16 extends above the flange 14. Thecylindrical body portion has two tubular openings 18, 20 (shown on FIG.3). Openings 18, 20 can be connected to a source of pressurised gas.Openings 18, 20 may be connected to supply pipes or lines that providepressurised gas to the insert 10. The source of pressurised gas may beany convenient source. The pressurised gas may be provided by a bloweror a compressor.

The insert 10 comprises an outer part 22 (shown in FIG. 7) and an innerpart 24 (shown in FIG. 6). The outer part includes the lower cylindricalprojection 12, the flange 14, the cylindrical body portion 16 and thetubular openings 18, 20. As can be seen from FIG. 7, the inner surface26 of outer part 22 of insert 10 forms a generally cylindrical surface.A plurality of keyways 28 are formed to extend upwardly from the loweredge of outer part 22 of insert 10. The keyways 28 are formed in threegroups that are spaced around the periphery of the lower edge of theouter part 22. Other arrangements may also be used.

The insert 10 also includes an inner part 24. Inner part 24 fits insideouter part 22 to form the insert 10. The inner part 24 has a cylindricallower region 30. Spaced projections 32 are formed on the cylindricallower region 30. Projections 32 are sized and positioned so that theycan fit into the keyways 28 formed on the lower edge of the outer part22 of the insert 10. In this manner, the outer part 22 and the innerpart 24 can be keyed together so that they are retained in positionrelative to each other (see FIG. 8). Other arrangements to position theinner part 24 relative to the outer part 22 may also be used. Indeed,the inner part 24 and the outer part 22 could be permanently affixed toeach other, such as by welding. As the cylindrical lower region 30 ofinner part 24 comes into contact with the cylindrical inner surface 26of the outer part 22 of the insert 10, a relatively sound seal can beachieved between the outer part 22 in the inner part 24. If desired,additional seals, such as O-rings or other seals, may be located betweenthe inner part 24 and the outer part 22 of the insert 10.

The inner part 24 includes a central waisted region (see FIG. 6). Thecentral waisted region includes an upper part 36 that extends inwardlyfrom an upper periphery 38 and a part that extends downwardly andoutwardly along region 40 (see FIG. 5). The transition from upper region36 to region 40 occurs via a smoothly curved surface 42. In this manner,the inner part 24 of arrangement 10 forms a venturi or a Coanda surfacethat is defined by the inner surfaces of regions 36, 40 and 42.

FIG. 5 shows a cross sectional view of the assembled insert 10. A plenumchamber 44 is defined between the outer surface of central waistedregion 34 of the inner part 24 and the inner surface of cylindrical bodyportion 16 of outer part 22. As can be seen from FIG. 5, the upperperiphery 38 (FIG. 6) of inner part 24 is spaced from an inwardlydirected surface 46 of outer part 22. The space that is defined betweenforms an open annular passage 48. Open annular passage 48 is in fluidcommunication with the plenum chamber 44 which, in turn, is in fluidcommunication with a source of compressed gas via tubular openings 18,20.

In use of the arrangement 10, pressurised gas is provided via tubularopenings 18, 20 to the plenum chamber 44. The compressed gas exits theplenum chamber 44 via the open annular passage 48. Due to the shape ofthe inner surface of the inner part 24, the gas flowing out of the openannular passage 48 tends to follow the inner surface of the inner part22, which causes the gas flowing out of the open annular passage 48 toflow downwardly and into the furnace. This also acts to entrain gas froman environment external to the furnace, which results in a total flow ofgas into the furnace that is significantly higher than the flow of gasarising from the gas leaving the open annular passage 48. The total flowof gas into the furnace is sufficient to prevent gas from the furnaceexiting through the feed opening of the furnace. In the embodiment shownin the attached drawings, the external gas that is entrained from theexternal environment largely or completely passes through the gap thatexists between the external surface of the frusto conical body 52 of thechute 50 and the upper part of the insert that extends inwardly anddownwardly from the upper periphery 58 of the insert.

It will be appreciated that the gas that flows into the furnace throughthe feed opening will ultimately exit the furnace through the exhaustopening of the furnace.

In order to enable feed materials to be fed to the furnace whilstminimising the risk that the feed materials will block the open annularpassage 48, the arrangement 10 may also be provided with a feed chute50. Feed chute 50 comprises a frusto conical hollow body 52 having aplurality of support feet 54 mounted thereto. Support feet 54 includerecesses 56 that are shaped to snugly fit onto the upper periphery 58 ofthe outer part 22 of insert 10. In other embodiments, the feed chute maybe permanently joined to the insert. In another embodiment, the feedchute may be omitted.

FIG. 9 shows a schematic cross-sectional view of a top entry submergedlance furnace 60. The furnace 60 includes a lower portion 62 thatcontains a bath of molten material. The top of the furnace includes afeed opening 64 and an exhaust opening 66. Exhaust gases are removedfrom the furnace through exhaust opening 66. Exhaust opening 66 islocated in a part of an exhaust region 68 of the furnace. The insert 10is inserted into the feed opening 64. Once inserted, the insert 10effectively forms the feed opening to the furnace.

FIG. 10 shows a schematic cross-sectional view of another top entrysubmerged lance furnace. The furnace 70 shown in in FIG. 10 has a numberof features that are in common with the furnace 60 shown in FIG. 9 and,for convenience, like features are denoted by the same referencenumerals as used in FIG. 10. Where the furnace 70 of FIG. 10 differsfrom the furnace 60 of FIG. 9 is that the furnace 70 of FIG. 10 includesa lance opening 72 having a lance 74 extending therethrough into thefurnace. Thus, the roof of the furnace 70 that is located away from theexhaust region of the furnace is provided with two separate openings,being the feed opening 64 and the lance opening 72.

Feed opening 64 is fitted with an arrangement 10 in accordance with thepresent invention to prevent egress of furnace contents from the feedopening 64. Similarly, lance opening 74 is also fitted with anarrangement 10 in accordance with the present invention to preventegress of furnace contents from the lance opening 74. In this regard,the arrangement 10 is effective to prevent egress of furnace contentsfrom the lance opening 72 even when the lance 74 extends through thelance opening 72. It will be appreciated that exhaust gas is removedfrom the furnace through exhaust opening 66, which causes the exhaustgas to flow into exhaust ducting/piping 76 to thereby remove the exhaustgas from the furnace. The exhaust ducting/piping may be provided withconventional exhaust gas cleaning systems, the nature of which will bewell understood by persons skilled in the art.

FIG. 11 shows a schematic cross-sectional view of another top entrysubmerged lance furnace. The furnace 80 shown in FIG. 11 is very similarto the furnace 70 shown in FIG. 10 in that it includes a feed opening 64and a lance opening 72. Other features that are common between thefurnace 80 of FIG. 11 in the furnace 70 of FIG. 10 are denoted by likereference numerals. Where the furnace 80 of FIG. 11 differs from thefurnace of FIG. 10 is that it is only the feed opening 64 of the furnace80 that is fitted with an arrangement 10 in accordance with the presentinvention. The lance opening 72 of the furnace 80 is simply providedwith conventional extraction systems (not shown) so that any dust orfurnace contents exiting the furnace through lance opening 72 arecaptured by the extraction systems and removed from the immediatelocation of the furnace. It will be appreciated that egress of dust orother furnace contents through feed opening 64 is prevented by operationof the arrangement 10 in accordance with the present invention. Theexhaust opening 66 is connected to exhaust ducting/piping 76 to therebyremove exhaust gas from the furnace.

FIG. 12 shows the results of modelling conducted on a top entrysubmerged lance furnace that is essentially similar to the furnace 70shown in FIG. 10. The furnace shown in FIG. 12 has a feed opening 64 anda lance opening 72. Exhaust piping 76 is also shown. The feed opening 64and the lance opening 72 are both provided with an arrangement 10 inaccordance with the present invention for preventing or minimisingegress of furnace contents therefrom. The modelling shown in FIG. 12shows gas flows when no flow of air is provided to the arrangements 10fitted into feed opening 64 and lance opening 72. As can be shown fromFIG. 12, significant plumes of gas exit the furnace from both the feedopening 64 and the lance opening 72.

FIG. 13 shows modelling of the furnace shown in FIG. 12 but with thedevices 10 fitted to the feed opening 64 and the lance opening 72,respectively, both being turned on so that air is flowing out of therespective passageways extending around the feed opening 64 and thelance opening 72 and into the furnace. As can be seen from FIG. 13,there is a significant inward flow of gas into the furnace through boththe feed opening 64 and the lance opening 72. The modelling shows thatthere is no egress of furnace contents through the feed opening 64 andthe lance opening 72 when the devices 10 in the feed opening 64 and thelance opening 72 are operating. The only gas exiting the furnace isexiting through the exhaust piping 76. Thus, operation of thearrangements 10 in accordance with the present invention has preventedegress of furnace contents through the feed opening 64 and lance opening72.

As shown in FIGS. 12 and 13, the present inventors have conducted CFDmodelling of a top entry submerged lance furnace having an insert 10present in the feed opening thereof. Absent the insert 10, or when theinsert 10 is not operating, that modelling shows that some of thegaseous contents of the furnace were emitted through the feed opening ofthe furnace. As the gaseous contents of the furnace may includecorrosive gases or toxic gases, it is undesirable that these gases beemitted through the feed opening, as operating personnel may be requiredto be in close physical proximity to the feed opening. The computermodelling conducted by the present inventors has shown that placing theinsert 10 in the feed opening and operating the insert 10 can preventthe egress of furnace gases from the furnace via the feed opening.

The skilled person will appreciate that the total flow of gas into thefurnace through the feed opening can be controlled by controlling theflow rate of gas leaving the annular passage in the insert. The flowrate of gas may be controlled by controlling the pressure of the gasthat is provided to the plenum chamber.

The amount of gas required to flow in through the feed opening toprevent furnace gases from leaving via the feed opening can also becontrolled by controlling the furnace pressure and/or controlling theflow rate of furnace gas leaving through the exhaust opening.

The gas that is supplied to the plenum chamber may comprise air.Alternatively the gas that is supplied to the plenum chamber maycomprise recycled furnace gas, recycled air, heated air, or even one ormore gases required to promote reactions within the furnace. Gases thatmay take part in reactions within the furnace include oxygen, carbonmonoxide, natural gas, other fuel gases or the like.

The temperature of the gas supplied to the plenum chamber may becontrolled to ensure that temperature conditions within the furnace arenot unduly upset.

The embodiment shown in the attached drawings includes two diametricallyopposed tubular inlets into the plenum chamber. It will be appreciatedthat a different number of inlets to the plenum chamber may be used toprovide pressurised gas to the plenum chamber. For example, for largerdiameter inserts, more than two openings into the plenum chamber may beprovided. Ideally, the plurality of openings to the plenum chamber willbe equi-spaced around the periphery of the plenum chamber.

The opening 48 through which the pressurised gas flows from the plenumchamber should be sized sufficiently large such that it is unlikely tobe blocked by stray particulate material that is being fed to thefurnace whilst also being small enough to ensure that a high gasvelocity is obtained in the gas leaving that passage.

The present invention has industrial applicability in respect of anyvessel that has a first opening and at least one other opening. It willbe appreciated that the gas that is injected into the vessel via thefirst opening must leave the vessel via another opening in order toenable the present invention to successfully operate.

Without wishing to be bound by theory, the present inventors believethat the present invention takes advantage of the Coanda effect. TheCoanda effect is the tendency of a jet of fluid, such as a jet of gas,to be attracted to and to flow along a nearby surface. By passingpressurised gas through the open annular passage, the pressurised gasleaving the annular passage tends to follow the surface of the waistedportion of the inner part of the insert. The waisted portion forms aCoanda surface (which has several characteristics of a venturi) and thepressurised gas leaving the open annular passageway flows inwardly andthen downwardly and along the inner surface of the waisted portion. Thisestablishes an inwardly directed flow of gas that has a relatively highspeed at a relatively low flow rate (that is, a relatively lowvolumetric flow rate). This causes external gas to also be drawn intothe waisted portion of the insert and thereafter into the furnace. Thetotal flow of gas through the insert into the furnace effectively formsan air curtain that acts to prevent furnace gases from flowing outthrough the feed opening.

The arrangement shown in the attached drawings may be retrofitted toexisting furnaces. The arrangement includes the outer part 22 and theinner part 24. In other embodiments, the outer part 22 and the innerpart 24 may be permanently joined together, such as by welding. However,the arrangement shown the attached drawings is advantageous in that theouter part 22 and the inner part 24 may be removed from the furnace andseparated from each other for cleaning or for clearing blockages. Itwill also be appreciated that a similar arrangement may be constructedas part of the feed opening of the furnace rather than being provided asa retrofit insert.

Although the preferred embodiment of the present invention has beendescribed with reference to its use in conjunction with a feed openingof a top entry submerged lance furnace, it will be appreciated that thepresent invention may be used in any application where a vessel isprovided with two or more openings and it is desired to prevent flow ofgas from the vessel out through one of those openings. The presentinvention may be used in other types of furnaces, in high-temperaturevessels, in storage vessels, such as storage silos for granular materialor particulate, and the like. The present invention can be used in anyapplication where it is desired to prevent the egress of gas, dust orfine particulate material from an opening of a vessel.

The present invention is also suitable for use with vessels where thefeed material is fed to the vessel through the first opening in acontinuous manner. In applications where the material is fed to thevessel in an intermittent manner, it may be possible to increase theflow of gas through the open passage when no feed material is being fedto the vessel in order to entrain sufficient gas from an externalenvironment to prevent egress of gas through the first opening.Alternatively, it may possible to simply close off the first openingusing a closure when no feed material is being fed to the vessel.

In the present specification and claims (if any), the word ‘comprising’and its derivatives including ‘comprises’ and ‘comprise’ include each ofthe stated integers but does not exclude the inclusion of one or morefurther integers.

Reference throughout this specification to ‘one embodiment’ or ‘anembodiment’ means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more combinations.

In compliance with the statute, the invention has been described inlanguage more or less specific to structural or methodical features. Itis to be understood that the invention is not limited to specificfeatures shown or described since the means herein described comprisespreferred forms of putting the invention into effect. The invention is,therefore, claimed in any of its forms or modifications within theproper scope of the appended claims (if any) appropriately interpretedby those skilled in the art.

The invention claimed is:
 1. A method for preventing egress of gas froma first opening of a vessel, the vessel including at least one otheropening through which gas can leave the vessel, the method comprisingsupplying a flow of gas to an open passage extending substantiallyaround the first opening and causing the flow of gas leaving the openpassage to flow towards and into the vessel whereby a gas from anenvironment external to the vessel is caused to be drawn into thevessel, wherein a total flow of gas into the first opening substantiallyprevents gas from leaving the vessel through the first opening.
 2. Anarrangement for preventing egress of a gas from a first opening of avessel, the vessel including at least one other opening through whichthe gas can leave the vessel, the arrangement comprising an open passageextending substantially around the first opening, the open passagereceiving a flow of gas such that the flow of gas leaves the openpassage and flows towards and into the vessel to cause a gas from theenvironment external to the vessel to be drawn into the vessel.
 3. Thearrangement as claimed in claim 2 wherein the open passage extendsaround the first opening.
 4. The arrangement as claimed in claim 2wherein the first opening comprises a generally circular opening.
 5. Thearrangement as claimed in claim 4 wherein the open passage comprises anannular open passage extending around the first opening.
 6. Thearrangement as claimed in claim 2 wherein the open passage extendsaround an inner surface of the first opening.
 7. The arrangement asclaimed in claim 2 wherein the surface of the first opening between theopen passage and the vessel is shaped to promote the flow of gas leavingthe open passage to flow towards and into the vessel.
 8. The arrangementas claimed in claim 7 wherein the surface of the first opening betweenthe open passage and the vessel have a shape, when moving in a directiontowards the vessel, that extends inwardly towards the centre of thefirst opening and then outwardly away from the centre of the firstopening.
 9. The arrangement as claimed in claim 2 wherein the surface ofthe first opening between the open passage and the vessel forms aventuri.
 10. The arrangement for preventing egress of a gas from a firstopening of a vessel as claimed in claim 2 wherein the surface of thefirst opening between the open passage and the vessel comprises a Coandasurface.
 11. The arrangement as claimed in claim 10 wherein the plenumchamber receives pressurised gas and the pressurised gas flows from theplenum chamber through the open passage and into the vessel.
 12. Thearrangement as claimed in claim 10 wherein the plenum chamber has atleast one, preferably two or more, inlets for receiving pressurised gas.13. The arrangement as claimed claim 12 wherein the plenum chamber hastwo or more inlets for receiving pressurised gas and the two or moreinlets are equi-spaced around the plenum chamber.
 14. The arrangement asclaimed in claim 2 wherein the open passage is in fluid communicationwith a plenum chamber.
 15. The arrangement as claimed in claim 14wherein the plenum chamber extends around the first opening.
 16. Thearrangement as claimed in claim 2 wherein the arrangement furthercomprises a feed chute for feeding material to the vessel.
 17. Thearrangement as claimed in claim 2 wherein the arrangement of the presentinvention comprises an insert that is inserted into the first opening ofthe vessel and when the insert is inserted into the first opening, theinner surface of the insert effectively defines the first opening of thefurnace.
 18. The arrangement as claimed in claim 17 wherein the insertincludes a portion extending into the first opening of the vessel andanother portion that defines the open passage extending around an innerperiphery of the insert.
 19. The arrangement as claimed claim 18,wherein the insert also defines the plenum chamber and at least oneinlet for receiving pressurised gas.
 20. The arrangement as claimed inclaim 17 wherein the insert comprises a flange that comes into contactwith an outer surface around the first opening of the vessel to therebyposition the insert relative to the first opening of the vessel.